In a new take on use of luminescent nanoparticles as cancer imaging probes, a team of investigators from several research institutes in Paris, France, has developed new metal-containing nanoparticles that emit light for several hours after they are initially excited. The researchers have demonstrated that once these nanoparticles are excited, they can then be injected into an animal and imaged without any additional energy input.

Reporting their work in the Proceedings of the National Academy of Sciences of the United States of America, Daniel Scherman, Ph.D., Quentin le Masne de Chermont, Ph.D., and colleagues describe their methods for synthesizing inorganic magnesium silicate-based nanoparticles doped with luminescent metals such as europium and dysprosium along with atoms of manganese. The particles range in diameter from 50 to 100 nanometers. Characterization experiments showed that the luminescent metal atoms concentrate in the center of the resulting nanoparticles together with the manganese atoms, forming an electronic core that can absorb light energy and emit red to near-infrared light for prolonged periods of time.

The investigators also developed chemical methods for modifying the surfaces of these nanoparticles. For this set of experiments, the investigators prepared nanoparticles whose surfaces were either positively charged, negatively charged, or had a neutral charge. They then energized the particles, injected the particles into animals, and monitored their distribution throughout the body in real time using near-infrared spectroscopic imaging. The investigators also used their persistently luminescent nanoparticles to image the new blood vessels surrounding tumors implanted in mice.

This work is detailed in the paper "Nanoprobes with near-infrared persistent luminescence for in vivo imaging." An abstract of this paper is available through PubMed.